This invention relates to an electrophotographic apparatus, for example, an electrophotographic printer, and a method for readily representing an image to be reproduced in continuous half-tones or gradations.
In prior art electrophotographic printers and copiers, half-tone printing was achieved by reducing the diameter of a bright spot illuminated on a photoconductive member by a source of light. This necessitated, however, an increase in the density of scanning lines so as to increase the density of picture elements in the printed image.
A drawback of this method for electrophotographically printing half-tone images is that when the diameter of the illuminated bright spot is sufficiently reduced, diffraction problems occur. Additionally, as the scan line density increases, the processing speed of the electrophotographic apparatus slows. Many attempts have been made to overcome these problems associated with the prior art techniques of electrophotographically printing half-tone images by reducing the diameter of the illuminated bright spot. However, until today, these attempts have been unsuccessful.